U.S. patent number 5,822,129 [Application Number 08/743,094] was granted by the patent office on 1998-10-13 for projection lens system.
This patent grant is currently assigned to Nikon Corporation. Invention is credited to Atushi Sekine.
United States Patent |
5,822,129 |
Sekine |
October 13, 1998 |
Projection lens system
Abstract
A projection lens system has a wide angle with small value for
back focus, superior telecentric characteristics, and small
distortion. The projection lens system includes a first lens group
having a negative refractive power and a second lens group having a
positive refractive power. The focal length of the entire system,
the focal length of the first lens group and the focal length of
the second lens group satisfy conditional formulas.
Inventors: |
Sekine; Atushi (Kasukabe,
JP) |
Assignee: |
Nikon Corporation (Tokyo,
JP)
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Family
ID: |
27295506 |
Appl.
No.: |
08/743,094 |
Filed: |
November 4, 1996 |
Foreign Application Priority Data
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Nov 7, 1995 [JP] |
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7-288305 |
Mar 12, 1996 [JP] |
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8-055137 |
Apr 9, 1996 [JP] |
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8-086764 |
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Current U.S.
Class: |
359/651; 359/649;
359/757; 359/764 |
Current CPC
Class: |
G02B
13/22 (20130101); G02B 13/04 (20130101); G02B
13/16 (20130101) |
Current International
Class: |
G02B
13/22 (20060101); G02B 13/16 (20060101); G02B
13/04 (20060101); G02B 021/02 () |
Field of
Search: |
;359/649-651,680-682,713-717,793,758,764,763,757 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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Hei 5-45582(A) |
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Feb 1993 |
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JP |
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Hei. 5-203871(A) |
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Aug 1993 |
|
JP |
|
Hei. 6-82690(A) |
|
Mar 1994 |
|
JP |
|
Hei. 6-148518(A) |
|
May 1994 |
|
JP |
|
Hei. 7-92385(A) |
|
Apr 1995 |
|
JP |
|
Hei. 7-253535(A) |
|
Oct 1995 |
|
JP |
|
Other References
English-language abstract of Hei 5-45582(A). .
English-language abstract of Hei. 5-203871(A). .
English-language abstract of Hei. 6-82690(A). .
English-language abstract of Hei. 6-148518(A). .
English-language abstract of Hei. 7-92385(A). .
English-language abstract of Hei. 7-253535(A)..
|
Primary Examiner: Epps; Georgia Y.
Assistant Examiner: Schwartz; Jordan M.
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A projection lens system for projecting an image from an image
display surface onto a screen, comprising in order from a screen
side of the projection lens system:
a first lens group having a negative refractive power and including
at least one lens;
a second lens group having a positive refractive power and
including at least two cemented lens components having cemented
surfaces with opposite signs for a radius of curvature of the
cemented surfaces; and
wherein a focal length f of the projection lens system, a focal
length f1 of the first lens group, and a focal length f2 of the
second lens group satisfy the following conditional formulas:
2. The projection lens system according to claim 1, wherein each of
the first lens group and the second lens group comprises at least
one aspherical lens.
3. The projection lens system according to claim 1, wherein a
distance D between the first lens group and the second lens group
and the focal length f1 of the first lens group satisfy the
conditional formula:
4.
4. The projection lens system according to claim 3, wherein the
first lens group comprises, in the following order from a screen
side, an aspherical positive lens and a negative lens.
5. The projection lens system according to claim 1, wherein the
first lens group comprises, in the following order from a screen
side, an aspherical positive lens and a negative lens.
6. A projection lens system for projecting an image from an image
display surface onto a screen, comprising in order from a screen
side of the projection lens system:
a first lens group having a negative refractive power and including
at least one lens;
a second lens group having a positive refractive power and
including at least one lens; and
wherein a focal length f of the projection lens system, a focal
length f1 of the first lens group, and a focal length f2 of the
second lens group satisfy the following conditional formulas:
and
0.5<.vertline.f1.vertline./f2<3,
and
the second lens group comprises, in the following order from a
screen side, an aspherical positive lens, a positive lens, and at
least two cemented lens components.
7. The projection lens system according to claim 6, wherein a
distance D between the first lens group and the second lens group
and the focal length f1 of the first lens group satisfy the
conditional formula:
8. The projection lens system according to claim 6, wherein the
first lens group comprises, in the following order from a screen
side, an aspherical positive lens and a negative lens.
9. A projection lens system for projecting an image from an image
display surface onto a screen, comprising in order from a screen
side of the projection lens system:
a first lens group having a negative refractive power and including
at least one lens;
a second lens group having a positive refractive power and
including at least one lens; and
wherein a focal length f of the projection lens system a focal
length f1 of the first lens group, and a focal length f2 of the
second lens group satisfy the following conditional formulas:
and
a distance D between the first lens group and the second lens group
and the focal length f1 of the first lens group satisfy the
conditional formula:
the first lens group comprises, in the following order from a
screen side, an aspherical positive lens and a negative lens,
and
a focal length f12 of the negative lens in the first lens group
satisfies the following conditional formula:
10. The projection lens system according to claim 9, wherein the
second lens group comprises a cemented lens.
11. A projection lens system for projecting an image from an image
display surface onto a screen, comprising in order from a screen
side of the projection lens system:
a first lens group having a negative refractive power and including
at least one lens;
a second lens group having a positive refractive power and
including at least one lens; and
wherein a focal length f of the projection lens system a focal
length f1 of the first lens group, and a focal length f2 of the
second lens group satisfy the following conditional formulas:
and
a distance D between the first lens group and the second lens group
and the focal length f1 of the first lens group satisfy the
conditional formula:
and
the second lens group comprises, in the following order from a
screen side, an aspherical positive lens, a positive lens, and a
cemented lens having a negative meniscus lens and a positive
lens.
12. The projection lens system according to claim 11, wherein a
focal length f22 of the positive lens satisfies the following
conditional formula:
13. The projection lens system according to claim 11, wherein a
focal length f23 of the cemented lens in the second lens group and
a focal length f22 of the positive lens satisfy the following
conditional formula:
14.
14. A projection lens system for projecting an image from an image
display surface onto a screen, comprising in order from a screen
side of the projection lens system:
a first lens group having a negative refractive power and including
at least one lens;
a second lens group having a positive refractive power and
including at least one lens; and
wherein a focal length f of the projection lens system, a focal
length f1 of the first lens group, and a focal length f2 of the
second lens group satisfy the following conditional formulas:
and
the first lens group comprises, in the following order from a
screen side, an aspherical positive lens and a negative lens,
and
the second lens group comprises, in the following order from a
screen side, an aspherical positive lens, a positive lens, and a
cemented lens having a negative meniscus lens and a positive
lens.
15. The projection lens system according to claim 14, wherein a
focal length f12 of the negative lens in the first lens group
satisfies the following conditional formula:
16. A projection lens system for projecting an image from an image
display surface onto a screen, comprising in order from a screen
side of the projection lens system:
a first lens group having a negative refractive power and including
at least one lens;
a second lens group having a positive refractive power and
including at least one lens; and
wherein a focal length f of the projection lens system a focal
length f1 of the first lens group, and a focal length f2 of the
second lens group satisfy the following conditional formulas:
and
and
the second lens group comprises, in the following order from a
screen side, an aspherical positive lens, a positive lens, and a
cemented lens having a negative meniscus lens and a positive
lens.
17. The projection lens system according to claim 16, wherein a
focal length f22 of the positive lens satisfies the following
conditional formula:
18.
18. The projection lens system according to claim 16, wherein a
focal length f23 of the cemented lens in the second lens group and
a focal length f22 of the positive lens satisfy the following
conditional formula:
19. A projection lens system, comprising in order from a screen
side:
a first lens group with a negative refractive power, disposed
closest to the screen side, and including a first aspherical lens
and a lens;
a second lens group with a positive refractive power, juxtaposed
the first lens group, and including a second aspherical lens and a
cemented lens;
wherein said first lens group has a first concave lens surface
facing toward the second lens group the first concave lens surface
is closest to said second lens group;
wherein said second lens group has a second concave lens surface
facing toward the first lens group the second concave lens surface
is closest to said first lens group; and
wherein a focal length f of the projection lens system, a focal
length f1 of the first lens group, a focal length f2 of the second
lens group, and a distance D between the first lens group and the
second lens group, satisfy the following conditions:
and
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection lens system to be
used for a projection apparatus which magnifies and projects an
image from a device such as a liquid crystal display (LCD) panel
onto a screen.
2. Description of Related Art
An apparatus which projects an image from a high-illumination CRT
on a screen by means of a projection lens system is known. However,
in recent years, an apparatus has been developed in which an image
on a liquid crystal display, instead of CRT, is magnified and
projected using a projection lens system.
A projection apparatus using a LCD panel is illustrated in FIG. 12.
In FIG. 12, a source light ray emitted from the light source 100 is
color separated by a dichroic mirror 101 which reflects red light
rays (R-rays) to separate the source light ray into R-rays and
light rays other than R-rays. The reflected R-rays are reflected by
a mirror 110, and then they enter a transmission type R-ray LCD
panel 120. The light ray transmitted through the mirror 101 is
color separated by a second dichroic mirror 102, which reflects
blue light rays (B-rays), to separate B-rays and green rays
(G-rays). The B-rays reflected by the mirror 102 enter a B-ray LCD
panel 121. The G-rays transmitted through the mirror 102 enter the
G-ray LCD panel 122. The light rays entering each color ray LCD
panel are modulated by the color signal of the respective colors in
each LCD panel, and only the modulated projection light is
transmitted. The R-rays and B-rays emitted from the R-ray LCD panel
120 and the B-ray LCD panel 121 are synthesized by a B-ray
reflecting dichroic mirror 103. The synthesized light is then
synthesized a second time with the G-rays emitted from the G-ray
LCD panel 122 and reflected by a G-ray reflecting dichroic mirror
104 to become a projection light. The projection light is projected
by a projection lens system 130 onto a screen.
A projection apparatus using the above-mentioned LCD panels, unlike
a projection apparatus using a CRT, is not capable of electrically
correcting distortion of the pictures in the projection image.
Moreover, only light rays emitted at a substantially vertical angle
with respect to the LCD panel may be used due to the angle
characteristic dependency of the liquid crystal.
Due to the problems mentioned above, the projection lens system for
a projection apparatus using LCD panels must have small distortion
and excellent telecentric properties in the LCD panel side.
A retrofocus type lens system having a front group of lenses with a
negative refractive power and a rear group of lenses with a
positive refractive power is conventionally known to project an
image from the above-mentioned LCD panels.
However, a retrofocus type lens system tends to produce off-axis
aberrations such as distortion, astigmatism and chromatic
aberration of magnification. Correction of these off-axis
aberrations is difficult when the F-number for the retrofocus type
lens is small.
When telecentric characteristics are provided in the retrofocus
type lens system to make the off-axis main light ray parallel to
the optical axis, the value for the back focus becomes too large,
causing the projection apparatus itself to be very large. Hence, in
order to produce a compact projection apparatus, it is necessary to
limit the back focus value within a certain range.
The LCD panels are typically driven by a matrix electrode.
Therefore, electrical correction of distortion of the projection
image is difficult. Thus, the distortion of the projection image is
mainly controlled by the construction of the projection lens
system.
The above problems have prevented the use of a wide angle
projection lens system to project images from LCD panels.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a compact, wide
angle projection lens system, having: a retrofocus type lens as a
basic structure, a small back focus value, excellent telecentric
characteristics, and small distortion.
According to a first aspect of the invention, in order to achieve
the above-mentioned object, the projection lens system of the
present invention comprises a first lens group having a negative
refractive power and a second lens group having a positive
refractive power. The focal length of the entire system (f), the
focal length of the first lens group (f1) and the focal length of
the second lens group (f2) satisfy the following conditional
formulas:
BRIEF DESCRIPTION OF THE DRAWINGS
A description of preferred embodiments of the invention will be
provided in conjunction with the following drawing figures,
wherein:
FIG. 1 is a cross section of a projection lens system of first
embodiment of the present invention;
FIG. 2 is a schematic view of a projection apparatus according to
the present invention;
FIG. 3 is a cross section of a projection lens system of a second
embodiment of the present invention;
FIG. 4 is a cross section of a projection lens system of a third
embodiment of the present invention;
FIG. 5 is a cross section of a projection lens system of a fourth
embodiment of the present invention;
FIG. 6 is a cross section of a projection lens system of a fifth
embodiment of the present invention;
FIG. 7 shows aberration diagrams for the projection lens system of
the first embodiment of the present invention;
FIG. 8 shows aberration diagrams for the projection lens system of
the second embodiment of the present invention;
FIG. 9 shows aberration diagrams for the projection lens system of
the third embodiment of the present invention;
FIG. 10 shows aberration diagrams for the projection lens system of
the fourth embodiment of the present invention;
FIG. 11 shows aberration diagrams for the projection lens system of
the fifth embodiment of the present invention; and
FIG. 12 is a schematic view of a known projection apparatus.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the present invention are described hereafter based
on the drawings. At the outset, the present invention will be
described with regard to the functional relationship between the
structure of the invention and the focal lengths of the various
lens groups.
FIG. 1 is a cross section of a projection lens system of a first
embodiment of the present invention. In FIG. 1, the projection lens
system comprises, in the following order from a screen side of the
system: a first lens group G1 having a negative refractive power,
an aperture diaphragm A, and a second lens group G2 having a
positive refractive power. The lens system projects, with a
predetermined magnification, an image displayed on an image forming
plane LC of a LCD panel.
In the projection lens system of the present invention, the focal
length of the entire system f, the focal length of the first lens
group f1 and the focal length of the second lens group f2 satisfy
the following conditional formulas (1) and (2):
If the value of .vertline.f1.vertline./f is larger than the upper
limit of conditional formula (1) above, the refractive power of the
first lens group G1 becomes undesirably weak, causing the size of
the first lens group G1 to be too large.
On the other hand, if the value of .vertline.f1.vertline./f is
smaller than the lower limit value of conditional formula (1), the
refractive power of the first lens group G1 becomes too strong,
causing barrel distortion of the projection lens system to be too
large, and making correction of distortion difficult. Moreover, if
the value of .vertline.f1.vertline./f is smaller than the lower
limit value of conditional formula (1), the back focus is
unnecessarily long, causing the size of the projection lens system
itself to be too large.
If the value of .vertline.f1.vertline./.vertline.f2.vertline. is
larger than the upper limit value of conditional formula (2), it is
necessary to increase the distance between the first lens group G1
and the second lens group G2 to correct image plane distortion. In
such a case, the first lens group G1 must be made large, resulting
in the problem of the entire lens system being too large.
On the other hand, if the value of
.vertline.f1.vertline./.vertline.f2.vertline. of the projection
lens system is smaller than the lower limit value of conditional
formula (2), the barrel distortion and the spherical aberration are
negatively large and correction is undesirably difficult.
Moreover, in the present invention, the distance D between the
first lens group G1 and the second lens group G2 and the focal
length of the first lens group f1 preferably satisfy the following
conditional formula:
If the value of D/.vertline.f1.vertline. is larger than the upper
limit value of conditional formula (3), correction of a chromatic
aberration of magnification is easy but the size of the first lens
group is undesirably large.
On the other hand, if the value of D/.vertline.f1.vertline. is
smaller than the lower limit value of conditional formula (3), the
size of the first lens group G1 is small, but correction of
distortion and correction of chromatic aberration of magnification
is undesirably difficult. In order to correct distortion here, the
system must be formed in such a manner that the shape of the
aspherical surface in the first lens group G1 possesses an
inflection point, which makes the manufacturing process undesirably
difficult.
In order to produce a favorable balance between correction of
on-axis chromatic aberration and correction of the chromatic
aberration of magnification, the second lens group G2 preferably
contains a cemented lens.
Furthermore, in the present invention, the first lens group G1
preferably comprises, in the following order from the screen side:
an aspherical positive lens L1 and a negative lens L2, as shown in
FIG. 1. The aspherical lens L1 is preferably made of resin. In the
above configuration, the focal length f1 of the first lens group G1
and the focal length f12 of the negative lens L2 in the first lens
group G1 preferably satisfy the following conditional formula:
Conditional formula (4) defines conditions to make the various
aberrations and paraxial amount difficult to vary even if the shape
of the aspherical lens made of resin used in the first lens group
G1 changes due to temperature fluctuation. If the value of
.vertline.f12.vertline./.vertline.f1.vertline. of the aspherical
lens L1 deviates from the range specified by conditional formula
(4), the refractive power of the aspherical lens L1 made of resin
is too large, causing fluctuation of various aberrations and
paraxial amounts. In particular, movement of the Gaussian image
plane is too large. As a result, when the temperature changes, the
focal position moves and a defocus condition occurs.
Moreover, the second lens group G2 preferably comprises, in the
following order from the screen side: an aspherical positive lens
L3, a positive lens L4, and a cemented lens with a negative
meniscus lens L5 and a positive lens L6.
The lenses L5 and L6 are placed in the cemented lens in such a
manner that on-axis chromatic aberration and chromatic aberration
of magnification are corrected simultaneously. This is accomplished
by placing the cemented lens L5, L6 at a position as far away as
possible from the diaphragm A, and close to the image forming plane
LC, and by making the RAND light ray (on-axis outermost light ray)
width large. On-axis chromatic aberration increases with the width
of the RAND light ray, and chromatic aberration of magnification
increases with the distance of the main light ray from the optical
axis.
The aspherical positive lens L3 of the second lens group G2 is
preferably made of resin. The focal length f2 of the second lens
group G2 and the focal length f22 of the positive lens L4
preferably satisfy the following conditional formula:
Conditional formula (5) defines a range in which the fluctuation of
various aberrations and the paraxial amount are controlled when the
shape of the aspherical lens L3 made of resin changes due to
temperature change. If the value of
.vertline.f22.vertline./.vertline.f2.vertline. deviates from the
range defined in formula (5), the refractive power of the
aspherical lens L3 made of resin is too large, causing fluctuation
of various aberrations and the paraxial amount. In particular, the
movement of the Gaussian image plane is large. Hence, the focal
position moves with the fluctuation of the temperature and a
defocus condition occurs.
The cemented lens L5, L6 is preferably structured to satisfy the
following conditional formula:
where f22 is a focal length of the positive lens L4 and f23 is a
focal length of the cemented lens L5, L6 in the second lens group
G2.
If the value of .vertline.f23.vertline./f22 is smaller than the
lower limit value of conditional formula (6), the refractive power
of the cemented lens L5, L6 is large. Accordingly, the refractive
power of the positive lens L4 is relatively small, making it
impossible to correct bow in the best image plane, which is
undesirable.
In a projection lens system configured to satisfy the
above-mentioned conditional formulas (1) and (2), it is preferred
for the second lens group G2 to comprise at least two cemented
lenses with opposite signs for the radius of curvature of the
cemented surfaces.
When two cemented lenses are configured such that the cemented
surfaces face opposite from each other, each lens is able to
contribute to the correction of on-axis chromatic aberration, while
keeping the radius of curvature of the cemented lenses small. One
advantage to such a configuration for the cemented lenses is that
they will be able to reduce chromatic aberration to a higher
degree. Moreover, because the cemented surfaces are facing in
opposite directions, the direction of chromatic aberration produced
by these cemented surfaces is opposite from each other. Hence, the
chromatic aberration of the cemented surfaces of the two cemented
lenses offset each other, reducing chromatic coma to a negligible
level.
A projection apparatus using a projection lens system of the first
embodiment of the present invention will be described hereafter
with reference to FIG. 2.
In FIG. 2, a white light ray emitted from a light source 10
contacts a cross dichroic mirror comprising a R-ray reflecting
dichroic mirror 11 and a B-ray reflecting dichroic mirror 12 placed
perpendicular to each other. The white light ray is color separated
by the cross dichroic mirror 11, 12 into R, G, and B-rays. The
R-rays enter the R-ray transmission type LCD panel 17 after being
reflected by the R-ray reflecting dichroic mirror 11 of the cross
dichroic mirror 11, 12 and being reflected by the mirrors 13 and
14. The B-ray enters the B-ray transmission type LCD panel 19 after
being reflected by the B-ray reflecting dichroic mirror 12 of the
cross dichroic mirror 11, 12 and being reflected by the mirrors 15
and 16. The G-rays transmit through the cross dichroic mirror 11,
12 and directly enter the G-ray transmission type LCD panel 18.
Each color ray LCD panel 17-19 displays image information. Light
rays transmitted from each of the color ray LCD panels 17-19 are
modulated according to the image information.
A cross dichroic prism 20, having R-ray reflecting dichroic film
20a and B-ray reflecting dichroic film 20b placed perpendicular to
each other, is placed on the transmission side of each color ray
LCD panels 17-19. The R-ray signal, which is the emitted R-ray
modulated by the R-ray transmission LCD panel 17, is reflected by
the R-ray reflecting dichroic film 20a and moves towards the
projection lens system 21. The B-ray signal, which is the emitted
B-ray modulated by the B-ray transmission LCD panel 19, is
reflected by the B-ray reflecting dichroic film 20b and moves
towards the projection lens system 21. The G-ray signal, which is
the emitted G-ray modulated by the G-ray transmission LCD panel 18,
transmits through the cross dichroic prism 20 and moves towards the
projection lens system 21. Each light signal from the cross
dichroic prism 20 is projected by the projection lens system 21
onto a screen (not shown), and a composite image of the images
displayed on each of light ray transmission type LCD panels 17-19
is formed on the screen.
Next, embodiments of the projection lens system of the present
invention will be described. FIG. 1 is a cross section of a
projection lens system according to a first embodiment of the
present invention, FIG. 3 is a cross section of a projection lens
system according to a second embodiment of the present invention,
FIG. 4 is a cross section of a projection lens system according to
a third embodiment of the present invention, FIG. 5 is a cross
section of a projection lens system according to a fourth
embodiment of the present invention, and FIG. 6 is a cross section
of a projection lens system according to a fifth embodiment of the
present invention.
The projection lens system in the first, second and third
embodiments comprises, in the following order from the screen side:
a first lens group G1 with a negative refractive power, an aperture
diaphragm A, and a second lens group G2 with a positive refractive
power. The projection lens system projects an image displayed on an
image forming plane LC of a LCD system onto a screen with
predetermined magnification. The first lens group G1 comprises, in
the following order from the screen side: an aspherical positive
lens L1 and a negative lens L2. The second lens group G2 comprises,
in the following order from the screen side: an aspherical positive
lens L3 having a meniscus shape with a concave surface facing the
screen side, a positive lens L4 having a surface with large
curvature on the image forming plane LC side, and a cemented lens
L5, L6 having a negative meniscus lens L5 with a convex surface
facing the screen side and a positive lens L6 having a convex
surface with large curvature on the screen side.
The projection lens system in the fourth embodiment, as shown in
FIG. 5, comprises, in the following order from the screen side: a
lens group G1 having a negative refractive power, an aperture
diaphragm A, and a second lens group G2 having a positive
refractive power. The projection lens system in the fourth
embodiment projects an image from the image forming plane LC of a
LCD system onto a screen with predetermined magnification. The
first lens group comprises, in the following order from the screen
side: an aspherical lens L1 and a negative lens L2. The second lens
group comprises, in the following order from the screen side: an
aspherical lens L3 having a meniscus shape with a concave surface
facing the screen side, a positive lens L4 having a convex surface
with strong curvature on the image forming plane LC side, a
cemented lens L5, L6 having a positive double convex lens L5 with
strong curvature on the LC side and a meniscus shape negative lens
L6 with a concave surface facing the screen side, and a cemented
lens L7, L8 having a meniscus shaped negative lens L7 with, a
concave surface facing the LC side and a positive meniscus shaped
lens L8 having a convex surface with a strong curvature on the
screen side.
The projection lens system in the fifth embodiments as shown in
FIG. 6, comprises, in the following order from the screen side: a
first lens group G1 having a negative refractive power, an aperture
diaphragm A, and a second lens group G2 having a positive
refractive power. The projection lens system in the fifth
embodiment projects an image displayed on an image forming plane LC
of a LCD system onto a screen with predetermined magnification. The
first lens group comprises, in the following order from the screen
side: an aspherical lens L1 and a negative lens L2. The second lens
group comprises, in the following order from the screen side: an
aspherical lens L3 having a meniscus shape with a concave surface
facing the screen side, a positive lens L4 having a convex surface
with strong curvature on the image forming plane LC side, a
cemented lens L5, L6 having a meniscus shape negative lens L5 with
the concave surface on the LC side and a meniscus shaped positive
lens L6 with a convex surface facing the screen side, and a
cemented lens L7, L8 having a double convex positive lens L7 with a
strong curvature on the LC side and a meniscus shaped negative lens
L8 with a concave surface facing the screen side.
In each of the embodiments, an aspherical lens made of acrylic is
used for both the aspherical positive lens L1 in the first lens
group G1 and for the aspherical positive lens L3 in the second lens
group G2. The aspherical positive lens L1 in the first lens group
G1 mainly corrects distortion and lowers coma aberration. The
aspherical positive lens L3 of the second lens group G2 mainly
corrects spherical aberration and upper coma aberration. In each of
the embodiments, aspherical lenses L1 and L3 are made of acrylic
resin having little refracting power to avoid movement of the focal
point caused by volume change, shape change, and change in the
refraction index of the acrylic resin due to heat and fluctuation
of temperature. A slight positive refracting power is retained to
correct focal point movement due to heat and temperature.
First Embodiment
In FIG. 1, the projection lens system of the first embodiment
comprises, in the following order from the screen side: a first
lens group G1 having a negative refractive power, a diaphragm A to
regulate the light ray which determines F-value and off-axis light
rays, and a second lens group G2 having a positive refractive
power. The first lens group G1 comprises, in the following order
from the screen side: an aspherical positive lens L1 having a
meniscus shape with a convex surface facing the screen side and a
negative meniscus lens L2 having a convex surface facing the screen
side. The second lens group G2 comprises, in the following order
from the screen side: an aspherical positive lens L3 having a
meniscus shape with the concave surface facing the screen sidle
wherein both surfaces have an aspherical shape, a positive lens L4
having a biconvex shape with a strong convex surface facing the
image display surface LC side, and a cemented lens L5, L6 having a
negative meniscus lens L5 with the convex surface facing the screen
side, and a positive meniscus lens L6 with the convex surface
facing the screen side, and a convex contact surface on the screen
side.
In each of Tables 1-5, f is the focal length of the entire
projection lens system, F is the F-number, 2.omega. is a total
field angle, and do is a distance from the screen to the first lens
surface. Moreover, in Tables 1-5, rj is the j-th radius of
curvature, dj is the distance from the j-th lens surface to the
subsequent lens surface, ni is the index of refraction of the
d-line in the i-th lens, and vi is the Abbe's number of the i-th
lens. Furthermore, aspherical lens surfaces are denoted by *
attached on the left of rj. The aspherical surface shape is
expressed by the equation (7) below. ##EQU1## Here, S is height
from the optical axis, X is the amount of sag at lens surface
height S, K is a conical constant, C is a curvature of the
reference spherical surface, and C2i (i=1, 5) is an aspherical
surface coefficient of degree 2i. In each of Tables 1-5, "x10-N"
means the Nth power of ten.
Various dimensions of the first embodiment are listed in Table
1.
TABLE 1 ______________________________________ f = 22.82 F/3.71
2.omega. = 77.6 d0 = 847.0 *r1 = 96.6983 d1 = 7.0000 n1 = 1.49108
.nu.1 = 57.57 *r2 = 98.0000 d2 = 3.0000 r3 = 414.2800 d3 = 2.0000
n2 = 1.51680 .nu.2 = 64.2 r4 = 23.7400 d4 = 65.0000 *r5 = 32.9281
d5 = 5.0000 n3 = 1.49108 .nu.3 = 57.57 *r6 = -30.0000 d6 = 6.0000
r7 = 509.6900 d7 = 17.0000 n4 = 1.61272 .nu.4 = 58.58 r8 = -33.0000
d8 = 10.0000 r9 = 64.8470 d9 = 1.5000 n5 = 1.84666 .nu.5 = 23.78
r10 = 24.2000 d10 = 14.5000 n6 = 1.61272 .nu.6 = 58.58 r11 =
380.0000 d11 = 41.3018 ______________________________________
Aspherical Surface Coefficients: L1 1st Surface K = 1.0 C2 = 0.0 C4
= 1.81510 .times. 10 -6 C6 = -9.36640 .times. 10 -10 C8 = 4.47650
.times. 10-14 C10 = 0.0 2nd Surface K = 1.0 C2 = 0.0 C4 = -2.79930
.times. 10-6 C6 = -9.43030 .times. 10 -10 C8 = 9.02580 .times.
10-13 C10 = 0.0 L3 5th Surface K = 1.0 C2 = 0.0 C4 = -3.96290
.times. 10-6 C6 = -4.61340 .times. 10-8 C8 = 2.30640 .times. 10-10
C10 = 0.0 6th S.nu.rface K = 1.0 C2 = 0.0 C4 = 7.58190 .times. 10-6
C6 = -1.07700 .times. 10-8 C8 = 1.59400 .times. 10-10 C10 = 0.0
______________________________________
Conditional Values for the First Embodiment:
.vertline.f1/f.vertline.=2.20
.vertline.f1/f2.vertline.=1.22
D/.vertline.f1.vertline.=1.29
.vertline.f12/f1.vertline.=0.97
.vertline.f22/f2.vertline.=1.23
.vertline.f23/f22.vertline.=10.03
Second Embodiment
In FIG. 3, the projection lens system of the second embodiment
comprises, in the following order from the screen side: a first
lens group G1 having a negative refractive power, a diaphragm A to
regulate the light ray which determines F-value and off-axis light
rays, and a second lens group G2 having a positive refractive
power.
As shown in FIG. 3, the first lens group G1 comprises, in the
following order from the screen side: an aspherical positive lens
L1 having a meniscus shape with the convex surface facing the
screen side and with the concave surface having an aspherical
shape, and a negative lens L2 having a biconcave shape with a
strong concave surface facing the image display surface LC side.
The second lens group G2 comprises, in the following order from the
screen side: an aspherical positive lens L3 having a meniscus shape
with a concave surface facing the screen side wherein both surfaces
have an aspherical shape, a positive lens L4 having a meniscus
shape with strong convex surface facing the image display surface
LC side, and a cemented lens L5, L6 having a negative meniscus lens
L5 with the convex surface facing the screen side, a positive lens
L6 having a biconvex shape, and a convex contact surface on the
screen side.
Various dimensions of the second embodiment are listed in Table
2.
TABLE 2
__________________________________________________________________________
f = 22.93 F/3.89 2.omega. = 78.1 d0 = 847.0 *r1 = 96.6983 d1 =
7.0000 n1 = 1.49108 .nu.1 = 57.57 *r2 = 200.0000 d2 = 3.0000 r3 =
-246.8121 d3 = 2.0000 n2 = 1.51680 .nu.2 = 64.1 r4 = 22.1791 d4 =
59.2000 *r5 = -50.0000 d5 = 5.0000 n3 = 1.49108 .nu.3 = 57.57 *r6 =
-30.0000 d6 = 6.0000 r7 = -69.5787 d7 = 17.0000 n4 = 1.61272 .nu.4
= 58.54 r8 = -38.7530 d8 = 10.0000 r9 = 288.4649 d9 = 1.5000 n5 =
1.84666 .nu.S = 23.82 r10 = 37.1886 d10 = 14.5000 n6 = 1.61272
.nu.6 = 58.54 r11 = -66.7328 d11 = 49.9098
__________________________________________________________________________
Aspherical Surface Coefficients: L1 1st Surface K = 1.0 C2 = 0.0 C4
= 4.48680 .times. 10-6 C6 = -1.54487 .times. 10-10 C8 = 9.73053
.times. 10-13 C10 = 0.0 2nd Surface K = 1.0 C2 = 0.0 C4 = -1.07038
.times. 10-6 C6 = -1.32558 .times. 10-9 C8 = 6.92432 .times. 10-13
C10 = 0.0 L3 5th Surface K = 1.0 C2 = 0.0 C4 = -1.98490 .times.
10-6 C6 = 2.90394 .times. 10-8 C8 = -4.26439 .times. 10-10 C10 =
0.0 6th Surface K = 1.0 C2 = 0.0 C4 = 1.81253 .times. 10-5 C6 =
3.10300 .times. 10-8 C8 = -1.45745 .times. 10-10 C10 = 0.0
__________________________________________________________________________
Conditional Values for the Second Embodiment:
.vertline.f1/f.vertline.=2.01
.vertline.f1/f2.vertline.=1.05
D/.vertline.f1.vertline.=1.30
.vertline.f12/f1.vertline.=0.86
.vertline.f22/f2.vertline.=1.59
.vertline.f23/f22.vertline.=2.38
Third Embodiment
In FIG. 4, the projection lens system of the third embodiment
comprises, similar to the first embodiment above, in the following
order from the screen side: a first lens group G1 having a negative
refractive power, a diaphragm A to regulate the light ray which
determines F-value and off-axis light rays, and a second lens group
G2 having a positive refractive power.
As shown in FIG. 4, the first lens group G1 comprises, in the
following order from the screen side: an aspherical positive lens
L1 having a meniscus shape with the convex surface facing the
screen side and both surfaces having an aspherical shape, and a
negative lens L2 having a meniscus shape with a convex surface
facing the screen side. The second lens group G2 comprises, in the
following order from the screen side: an aspherical positive lens
L3 having a meniscus shape with a concave surface facing the screen
side wherein both surfaces have an aspherical shape, a positive
lens L4 having a biconvex shape with strong convex surface facing
the image display surface LC side, and a cemented lens L5, L6
having a negative meniscus lens L5 with the convex surface facing
the screen side, and a positive meniscus lens L6 with a convex
contact surface on the screen side.
Various dimensions of the third embodiment are listed in Table
3.
TABLE 3
__________________________________________________________________________
f = 22.93 F/3.71 2.omega. = 77.4 d0 = 847.0 *r1 = 120.0000 d1 =
7.0000 n1 = 1.49108 .nu.1 = 57.57 *r2 = 95.0000 d2 = 3.0000 r3 =
128.0936 d3 = 2.0000 n2 = 1.46450 .nu.2 = 65.77 r4 = 25.0438 d4 =
61.0000 *r5 = -30.0000 d5 = 5.0000 n3 = 1.49108 .nu.3 = 57.57 *r6 =
-35.0000 d6 = 6.0000 r7 = 2958.7019 d7 = 17.0000 n4 = 1.69680 .nu.4
= 55.60 r8 = -31.7573 d8 = 10.0000 r9 = 48.9228 d9 = 1.5000 n5 =
1.860741 .nu.5 = 23.01 r10 = 21.5651 d10 = 18.0000 n6 = 1.696800
.nu.6 = 55.60 r11 = 82.2723 d11 = 32.2606
__________________________________________________________________________
Aspherical Surface Coefficients: L1 1st Surface K = 1.0 C2 = 0.0 C4
= 1.7248 .times. 10-6 C6 = -9.84819 .times. 10-10 C8 = 6.85046
.times. 10-13 C10 = 0.0 2nd Surface K = 1.0 C2 = 0.0 C4 = -2.21633
.times. 10-6 C6 = -7.99371 .times. 10-11 C8 = 6.54207 .times. 10-13
C10 = 0.0 L3 5th Surface K = 1.0 C2 = 0.0 C4 = 1.34920 .times. 10-5
C6 = -6.87413 .times. 10-8 C8 = 2.29989 .times. 10-10 C10 = 0.0 6th
Surface K = 1.0 C2 = 0.0 C4 = 2.23589 .times. 10-5 C6 = 2.07873
.times. 10-9 C8 = 7.51985 .times. 10-11 C10 = 0.0
__________________________________________________________________________
Conditional Values for the Third Embodiment:
.vertline.f1/f.vertline.=2.01
.vertline.f1/f2.vertline.=1.73
D/.vertline.f1.vertline.=0.95
.vertline.f12/f1.vertline.=1.05
.vertline.f22/f2.vertline.=1.22
.vertline.f23/f22.vertline.=8.33
Fourth Embodiment
In FIG. 5, the projection lens system of the fourth embodiment
comprises, in the following order from the screen side: a first
lens group G1 having a negative refractive power, a diaphragm A to
regulate the light ray which determines F-value and off-axis light
rays, and a second lens group G2 having a positive refractive
power.
As shown in FIG. 5, the first lens group G1 comprises, in the
following order from the screen side: an aspherical positive lens
L1 having a meniscus shape with a convex surface facing the screen
side and both surfaces being aspherical in shape, and a negative
meniscus lens L2 having the convex surface facing the screen side.
The second lens group G2 comprises, in the following order from the
screen side: an aspherical positive lens L3 having a meniscus shape
with the concave surface facing the screen side wherein both
surfaces are aspherical in shape, a positive lens L4 with a strong
convex surface facing the image display surface LC side, a cemented
lens L5, L6 having a biconvex shape positive lens L5 with the
convex surface with stronger curvature facing the image display
surface LC side and a negative meniscus lens L6 with the concave
surface facing the screen side, and a cemented lens L7, L8 having a
negative meniscus lens L7 with the concave surface facing the image
display surface LC side, and a meniscus shaped positive lens L8
with the convex contact surface facing the screen side. In FIG. 5,
a glass parallel flat board B, which is equivalent to a color
combination dichroic prism, is shown located on the image display
surface LC side of the second lens group G2.
Various dimensions of the fourth embodiment are listed in Table
4.
TABLE 4
__________________________________________________________________________
f = 22.93 F/3.59 2.omega. = 72.1 d0 = 225.9 *r1 = 97.6100 d1 =
7.0000 n1 = 1.49084 .nu.1 = 57.07 *r2 = 98.0000 d2 = 5.0000 r3 =
128.0790 d3 = 2.0000 n2 = 1.51633 .nu.2 = 64.14 r4 = 20.3500 d4 =
58.0000 *r5 = -32.9281 d5 = 5.0000 n3 = 1.49084 .nu.3 = 57.07 *r6 =
-30.0000 d6 = 6.0000 r7 = -471.0000 d7 = 15.0000 n4 = 1.612713
.nu.4 = 58.75 r8 = -30.5900 d8 = 7.0000 r9 = 374.0530 d9 = 12.0000
n5 = 1.612713 .nu.S = 58.75 r10 = -35.0800 d10 = 2.0000 n6 =
1.755203 .nu.6 = 27.51 r11 = -208.9400 d11 = 0.2000 r12 = 73.9000
d12 = 2.0000 n7 = 1.755203 .nu.7 = 27.51 r13 = 35.0800 d13 = 8.5000
n8 = 1.612713 .nu.8 = 58.75 r14 = 173.6600 d14 = 6.0922 r15 =
0.0000 d15 = 41.61 n9 = 1.620046 .nu.9 = 36.30 r16 = 0.0000 d16 =
9.9496
__________________________________________________________________________
Aspherical Surface Coefficients: L1 1st Surface K = 1.0 C2 = 0.0 C4
= 7.32880 .times. 10-6 C6 = -2.91730 .times. 10-9 C8 = 2.28860
.times. 10-12 C10 = 0.0 2nd Surface K = 1.0 C2 = 0.0 C4 = 4.62870
.times. 10-6 C6 = -4.12870 .times. 10-9 C8 = 9.29860 .times. 10-13
C10 = 0.0 L3 Sth Surface K = 1.0 C2 = 0.0 C4 = -5.64200 .times.
10-6 C6 = -1.92040 .times. 10-8 C8 = 8.94830 .times. 10-11 C10 =
0.0 6th Surface K = 1.0 C2 = 0.0 C4 = 6.49150 .times. 10-6 C6 =
9.57310 .times. 10-9 C8 = 8.69190 .times. 10-11 C10 = 0.0
__________________________________________________________________________
Conditional Values for the Fourth Embodiment:
.vertline.f1/f.vertline.=2.14
.vertline.f1/f2.vertline.=1.23
D/.vertline.f1.vertline.=1.18
.vertline.f12/f1.vertline.=0.97
.vertline.f22/f2.vertline.=1.32
Fifth Embodiment
In FIG. 6, the projection lens system of the fifth embodiment
comprises, in the following order from the screen side: a first
lens group G1 having a negative refractive power, a diaphragm A to
regulate the light ray which determines the F-value and off-axis
light rays, and a second lens group G2 having a positive refractive
power.
As shown in FIG. 6, the first lens group G1 comprises, in the
following order from the screen side: an aspherical positive lens
L1 having a meniscus shape with the convex surface facing the
screen side and both surfaces being aspherical in shape, and a
negative meniscus lens L2 having the convex surface facing the
screen side. The second lens group G2 comprises, in the following
order from the screen side: an aspherical positive lens L3 having a
meniscus shape with the concave surface facing the screen side
wherein both surfaces are aspherical in shape; a positive lens L4
with a stronger convex surface facing the image display surface LC
side; a cemented lens L5, L6 having a meniscus shape negative lens
L5 with the concave surface facing the image display surface LC
side, and a positive meniscus lens L6 with the convex contact
surface facing the screen side; and a cemented lens L7, L8 having a
biconvex shaped positive lens L7 with the stronger convex surface
facing the image display surface LC side, and meniscus shaped
negative lens L8 with a concave contact surface facing the screen
side. In FIG. 6, a glass parallel flat board B, which is equivalent
to a color combination dichroic prism, is also shown.
Various dimensions of the fifth embodiment are listed in Table
5.
TABLE 5
__________________________________________________________________________
f = 22.93 F/3.62 2.omega. = 72.3 d0 = 230.5 *r1 = 96.6983 d1 =
7.0000 n1 = 1.49084 .nu.1 = 57.07 *r2 = 98.0000 d2 = 5.0000 r3 =
179.0926 d3 = 2.0000 n2 = 1.516799 .nu.2 = 64.20 r4 = 21.0544 d4 =
58.0000 *r5 = -32.9281 d5 = 5.0000 n3 = 1.49084 .nu.3 = 57.07 *r6 =
-30.0000 d6 = 6.0000 r7 = -413.4146 d7 = 15.0000 n4 = 1.612716 `)4
= 58.58 r8 = -30.4879 d8 = 5.0000 r9 = 86.3419 d9 = 2.0000 n5 =
1.755204 .nu.5 = 27.53 r10 = 33.0000 d10 = 7.0000 n6 = 1.612716
.nu.6 = 58.58 r11 = 51.6689 d11 = 5.0000 r12 = 56.5014 d12 =
15.0000 n7 = 1.612716 .nu.7 = 58.58 r13 = -37.0000 d13 = 2.0000 n8
= 1.755204 .nu.8 = 27.53 r14 = -155.2089 d14 = 6.0000 r15 = 0.0000
d15 = 40.0000 n9 = 1.620046 .nu.9 = 36.30 r16 = 0.0000 d16 = 9.3004
__________________________________________________________________________
Aspherical Surface Coefficients: L1 1st Surface K = 1.0 C2 = 0.0 C4
= 8.55340 .times. 10-6 C6 = -4.21230 .times. 10-9 C8 = 3.16030
.times. 10-12 C10 = 0.0 2nd Surface K = 1.0 C2 = 0.0 C4 = 6.58910
.times. 10-6 C6 = -7.36740 .times. 10-9 C8 = 2.426500x10-12 C10 =
0.0 L3 Sth Surface K = 1.0 C2 = 0.0 C4 = -1.02430 .times. 10-5 C6 =
-2.80120 .times. 10-8 C8 = 1.13110 .times. 10-10 C10 = 0.0 6th
Surface K = 1.0 C2 = 0.0 C4 = 4.17350 .times. 10-6 C6 = 3.76070
.times. 10-9 C8 = 1.13480 .times. 10-10 C10 = 0.0
__________________________________________________________________________
Conditional Values for the Fifth Embodiment:
.vertline.f1/f.vertline.=2.09
.vertline.f1/f2.vertline.=1.17
D/.vertline.f1.vertline.=1.21
.vertline.f12/f1.vertline.=0.97
.vertline.f22/f2.vertline.=1.29
FIGS. 7-11 show various aberrations of the projection systems of
the first through fifth embodiments, respectively. In the diagrams,
NA denotes the number of apertures in the screen side, Y denotes
the image height at the image display surface LC side, and d
denotes the d-line (.lambda.=587.6 nm). Moreover, the sine
condition is represented by a broken line in the spherical
aberration diagram. In the astigmatism diagram, the meridional
image surface is represented by a broken line and the sagittal
image surface is represented by a continuous line.
As shown in FIGS. 7-9, although the entire field angle achieves a
wide field angle of about 72.degree., the value of back focus is
small at about 32 mm-50 mm, demonstrating a superior optical
performance for the present invention.
Accordingly, miniaturization of the entire projection apparatus can
be achieved without sacrificing superior optical performance over a
wide field angle.
As explained above, the present invention provides a compact
projection lens system with small value of back focus, a wide
angle, superior telecentric characteristics, and small distortion.
Moreover, the present invention achieves superior optical
performance over a wide field angle and enables miniaturization of
the entire projection apparatus.
While this invention has been described in conjunction with
specific embodiments thereof, it is evident that many alternatives,
modifications and variations will be apparent to those skilled in
the art. Accordingly, the preferred embodiments of the invention as
set forth herein are intended to be illustrative, not limiting.
Various changes may be made without departing from the spirit and
scope of the invention as defined in the following claims.
* * * * *